Reinforced Performance of Lead-free Sn-8Zn-3Bi Solder With Doping of 0.03 wt. C_(60) on Cu Pads

摘要

In this study, 0.03 wt.% C_(60) was doped into lead-free Sn-8Zn-3Bi solder by mechanically dispersing. The reinforced solder has been widely investigated under a current density of 3.5×10~3 A/cm~2 at 100°C for 180 hours. The interfacial morphologies and microstructures of the plain and doped Sn-8Zn-3Bi solder on Cu pads on daisy chain type ball grid array(BGA) substrates were systematically analyzed by SEM/EDX. It was found that C_(60) doped solder has well refined microstructure and the C_(60) dopant inhibited the Cu_5Zn_8 intermetallic compound (IMC) growth. Melting characteristic and mechanical property evaluation were also carried out. From differential scanning calorimetry (DSC) studies, the melting characteristic of the doped solders differed little from the plain solder. The shear strength and hardness of solder joints were substantially improved with the addition of C_(60). Moreover, shear fracture occurs at the IMC interfacial region during shear testing. The observed ductile fracture mode with a rough dimpled surface is attributed to a second phase dispersion strengthening mechanism.